This invention relates to a novel adhesive composition and an adhesive sheet on which the composition is coated. The adhesive composition and the adhesive sheet have excellent heat resistance, moisture resistance, chemical resistance, flexibility, workability, molding property and storage stability.
U.S. Pat. No. 4,110,364 discloses curable resin compositions comprising a cyanate ester compound, and a polyfunctional maleimide, and optionally an epoxy resin or other thermosetting resin monomer or prepolymer. U.S. Pat. No. 3,562,214 discloses curable resin compositions comprising a cyanate ester compound and an epoxy resin.
Incorporation of butadiene-acrylonitrile compolymer into the above polyvinyl acetate into the above compositions (Japanese Patent Publication (kokoku) No. 40179/1982), incorporation of dimer acid-based polyamide into the above compositions, (Japanese Patent Publication (kokai) No. 206673/1983), incorporation of 1,2-polybutadiene rubber into the above compositions (U.S. Pat. No. 4,404,330) and incorporation of acryl rubber into the above compositions (U.S. Pat. No. 4,396,745) were also known.
The resin composition into which butadiene-acrylonitrile copolymer, polyvinyl acetate, or dimer acid-based polymer is incorporated have somewhat poor adhering property and moisture resistance in normal state. The resin composition into which thermoplastic polyurethane is incorporated has somewhat poor moisture resistance, and compatibility of the polyurethane to the resin composition is insufficient, and long time storage stability of the composition is bad.
On the other hand adhesive compositions comprising polyester resin itself which is either non-crystalline or of low crystallinity, (i.e., essentially amorphous), or adhesive compositions comprising the polyester and epoxy resin were known. Although these composition have excellent adhering property and flexibility, they are poor in respect of heat resistance, bonding force at elevated temperature and hardness.